Large Input/Output Connectors
The great progress realized these last years in the data processing technology now allows the interconnection of numerous sub-systems with a constantly growing number of input and output signals. The reduction of the overall size of connectors leads to increase of the density of both pins and contacts. However, higher is the number of transmitted signals per connection, more fragile and thinner are the pins and contacts. The standard connectors which are the most frequently used, are manually inserted. The retention of the cable connector is done mainly by means of mechanical devices such as screws, springs, embossing or different kinds of latching.
Inserting Force
FIGS. 1 to 4 show an overview of the particular problems encountered by the plugging and unplugging of large cable connectors. Large cable connectors (1) (more than 80 pins) are very often designed as an extension of small size connectors which, as for them, can be easily plugged and unplugged manually. But the insertion force is directly related to number of pins.
The improvement of the Radiated Frequency Interference (RFI), Electro-Static Discharge (ESD), Electrical Fast Transient (EFT) behaviour of large connectors requires additional contacts between male and female shells (16). These contacts are achieved due to special embossing or springs on the male shell which also have, by sliding friction, the adverse effect of drastically increasing the insertion force.
Therefore, it becomes very difficult for an operator to smoothly insert and remove such assemblies. As described in FIG. 2, the operator is forced to plug and unplug the pins sequentially, by applying a kind of wavy motion. But, since the pins are very fragile, this kind of un-straight motion may lead to contact damages (6) and indirectly to machines misfunctions as show in FIG. 4.
The connector latching systems very often increases the above problem. As shown in FIG. 1, the retention system, the most frequently used, consists of a couple of screws (3) which fit in threaded studs (4) on the receiving connector (2). Most of time, the operator does not have the force to plug completely the connector and to complete the job, he uses the retention screws (3) or other plugging tools. Instead of turning the two screws at the same time, the operator tightens screws one after the other, which does not move the cable connector straightly, but with an angle as shown in FIG. 3. Pins follow the same motion and go in sockets with a wrong orientation which bends pins (5) and opens female sockets (6) (FIG. 4).
A system adapted to connectors having a small number of I/O is not endlessly expendable to large connectors. There is a limit which depends upon several different parameters:
connector shape, PA1 accessibility, PA1 contact technology, PA1 operator, PA1 etc. PA1 guide the cable and receiving connectors, PA1 multiply the operator's insertion/extraction force and PA1 center the forces on the connectors axis.
To give an approximate limit, when the insertion force is above approximately 20 kg, an assisted device is highly recommended for plugging or unplugging male and female connectors.